Annulated tubular structure intended for transporting fuel into the tank

ABSTRACT

A partially annulated flexible tubular structure located at least partially inside the fuel tank, of a vehicle, the structure being capable of being at least partially submerged in the tank and being intended for transporting the fuel into the tank, the tubular structure including at least one layer (1) including a composition including: a. between 39% and 100% by weight, in particular between 41% and 100% by weight, of at least one aliphatic polyamide of formula W/Z, b. between 0% and 4% by weight, and preferably between 0 and 2%, of at least one plasticizer, c. between 0% and 20% of at least one impact modifier, d. between 0% and 37% by weight of at least one additive, the sum of a.+b.+c.+d. being equal to 100% of the total weight of the composition, excluding a fuel transport structure running from the tank to the motor of the vehicle.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/967,481, filed on Aug. 5, 2020, which is a US National Stage of PCTApplication No. PCT/FR2019/050365, filed on Feb. 19, 2019, which claimsthe benefit of French Application No. FR 1851461, filed on Feb. 21,2018. The entire contents of each of U.S. application Ser. No.16/967,481, PCT Application No. PCT/FR2019/050365, and FrenchApplication No. FR 1851461 are hereby incorporated by reference.

TECHNICAL FIELD

The invention relates to a partially annulated flexible tubularstructure for transporting a fuel, in particular gasoline or diesel,particularly gasoline, into the tank of a motor vehicle.

More particularly, the invention relates to a monolayer or multilayertubular structure being at least partially located inside the fuel tankand being capable of being at least partially submerged in the vehicletank.

Said monolayer or multilayer tubular structure is therefore intended tobe at least partially inside the fuel tank and is capable of being atleast partially submerged in the tank of the vehicle.

BACKGROUND

Fuels currently used in motor vehicles increasingly include corrosivecompounds such as methanol or ethanol.

Alcoholic compounds as well as other compounds present in the fuelstransported cause the dissolution and diffusion of chemicals,particularly monomers and oligomers derived from the tube in contactwith gasoline, the tube typically consisting of aliphatic materials suchas aliphatic polyamides such as PA 11 or PA 12.

Vehicle manufacturers are becoming increasingly demanding about theamount of extractables such as monomers/oligomers dissolved in gasoline,which are more likely to clog injectors.

In accordance with U.S. Pat. No. 5,076,329, a layer of PA 6 as an innerlayer makes it possible to at least partially eliminate the problem ofexcess of extractables, which would occur with PA 12 in the inner layerof a gasoline transport tube comprising five layers. The use of afive-layer system makes it possible to obtain a tube with PA 12 impactresistance with a low level of monomers/oligomers.

Nevertheless, in accordance with document WO 94/09303, thesecharacteristics cannot be obtained with a tube comprising less than fivelayers.

This document then recommends the use of a partially annulated two-layeror three-layer tube comprising, for the two-layer structure, an outerlayer, which may be made of PA 11 or PA 12, and an inner layer, which isnot made of polyamide and is selected from fluorinated compounds such asPVDF. In the context of the three-layer structure, a bonding layer,particularly made of PVDF, is then introduced between the outer layerand the inner layer.

However, these tubes have an operating temperature between −40° C. and150° C., and are used for vehicle motors.

EP 1039199 discloses partially annulated tubes for use in transportinggasoline comprising at least two layers, an outer layer of polyamide andan inner layer of tetrafluoroethylene-hexafluoropropylene-vinylidenefluoride (THV).

Nevertheless, this document specifies that the outer layer protects thetube, for example, from the impact caused by a stone when the car isrunning and that it is preferable for the resin to have a certain levelof resistance to elongation and impact, which implies that the use ofthis tube is intended for transporting gasoline from the tank or intothe motor.

For use of the tube in the tank of the vehicle, it is thereforenecessary to have a tube available, which, although capable of being atleast partially submerged in the fuel of the vehicle, has an amount ofextractables, which is less than that of the tubes of the background arthereinbefore and meets the requirements of the manufacturers.

SUMMARY

This has been solved by the partially annulated flexible structure ofthe invention.

The present invention therefore relates to a partially annulatedflexible tubular structure located at least partially inside the fueltank, in particular the gasoline or diesel tank, particularly thegasoline tank, of a vehicle, said structure being capable of being atleast partially submerged in said tank and being intended fortransporting said fuel into said tank, said tubular structure comprisingat least one layer (1) comprising a composition comprising:

-   -   a. between 39% and 100% by weight, in particular between 41% and        100% by weight, of at least one aliphatic polyamide of formula        W/Z wherein:    -   W is an aliphatic repeating unit obtained from the        polycondensation of at least one C6-C18 lactam, preferably        C7-C13 lactam, or at least one C6-C18 aminocarboxylic acid,        preferably C7-C13 aminocarboxylic acid, or is an aliphatic        repeating unit XY having an average number of carbon atoms per        denoted nitrogen atom ranging from 6 to 18, preferably from 7 to        13, obtained from the polycondensation:    -   at least one C6-C18 diamine X, said diamine being selected from        a linear or branched aliphatic diamine or a mixture thereof, and    -   at least one C6-C18 aliphatic dicarboxylic acid Y,    -   Z is at least one optional polyamide repeating unit, Z being        able to be present at up to 30% by weight relative to the total        weight W/Z, preferably up to 15% by weight relative to the total        weight W/Z,    -   b. between 0% and 4% by weight, preferably between 0 and 2%, of        at least one plasticizer,    -   c. between 0% and 20% of at least one impact modifier,    -   d. between 0% and 37% by weight of at least one additive,    -   the sum of a.+b.+c.+d. being equal to 100%,    -   excluding a fuel transport structure running from the tank to        the motor of the vehicle.

In other words, said structure is intended to be placed at leastpartially inside the fuel tank.

The inventors have therefore found that a tubular structure comprising alayer comprising a particular composition as defined hereinbefore madeit possible to greatly reduce the amount of extractables andparticularly the “solubles” and thus meet the requirements of anextractable test by a motor vehicle manufacturer.

The term “flexible” means that the deformation and extension ability ofthe tubular structure make it possible to form relatively small anglesmaking it possible to adapt the tubular structure to a limited spacedelimited by the fuel tank.

The expression “being located at least partially inside the tank” meansthat preferably more than 70%, more preferably more than 90%, even morepreferably more than 95%, and particularly 100% of the total length ofthe tube is located in the tank, part of the said tube being able toleave the said tank in order to adapt to a tube for transportinggasoline between the tank and the motor, particularly by means of aconnector.

In one embodiment, said tubular structure comprises at least one layer(1) comprising a composition consisting of:

-   -   a. between 39% and 100% by weight, in particular between 41% and        100% by weight, of at least one aliphatic polyamide of formula        W/Z wherein:    -   W is an aliphatic repeating unit obtained from the        polycondensation of at least one C6-C18 lactam, preferably        C7-C13 lactam, or at least one C6-C18 aminocarboxylic acid,        preferably C7-C13 aminocarboxylic acid, or is an aliphatic        repeating unit XY having an average number of carbon atoms per        denoted nitrogen atom ranging from 6 to 18, preferably from 7 to        13, obtained from the polycondensation:    -   at least one C6-C18 diamine X, said diamine being selected from        a linear or branched aliphatic diamine or a mixture thereof, and    -   at least one C6-C18 aliphatic dicarboxylic acid Y,    -   Z is at least one optional polyamide repeating unit, Z being        able to be present at up to 30% by weight relative to the total        weight W/Z, preferably up to 15% by weight relative to the total        weight W/Z,    -   b. between 0% and 4% by weight, preferably between 0 and 2%, of        at least one plasticizer,    -   c. between 0% and 20% by weight of at least one impact modifier,    -   d. between 0% and 37% by weight of at least one additive,    -   the sum of a.+b.+c.+d. being equal to 100% of the total weight        of the composition,    -   excluding a fuel transport structure running from the tank to        the motor of the vehicle.

There are therefore no constituents in said composition other thanconstituents a, b, c, and d, the sum of which is equal to 100% byweight.

In another embodiment, said tubular structure comprises at least onelayer (1) consisting of a composition consisting of:

-   -   a. between 39% and 100% by weight, in particular between 41% and        100% by weight, of at least one aliphatic polyamide of formula        W/Z wherein:    -   W is an aliphatic repeating unit obtained from the        polycondensation of at least one C6-C18 lactam, preferably        C7-C13 lactam, or at least one C6-C18 aminocarboxylic acid,        preferably C7-C13 aminocarboxylic acid, or is an aliphatic        repeating unit XY having an average number of carbon atoms per        denoted nitrogen atom ranging from 6 to 18, preferably from 7 to        13, obtained from the polycondensation:    -   at least one C6-C18 diamine X, said diamine being selected from        a linear or branched aliphatic diamine or a mixture thereof, and    -   at least one C6-C18 aliphatic dicarboxylic acid Y,    -   Z is at least one optional polyamide repeating unit, Z being        able to be present at up to 30% by weight relative to the total        weight W/Z, preferably up to 15% by weight relative to the total        weight W/Z,    -   b. between 0% and 4% by weight, preferably between 0 and 2%, of        at least one plasticizer,    -   c. between 0% and 20% by weight of at least one impact modifier,    -   d. between 0% and 37% by weight of at least one additive,    -   the sum of a.+b.+c.+d. being equal to 100% of the total weight        of the composition,    -   excluding a fuel transport structure running from the tank to        the motor of the vehicle.

The layer (I) in this embodiment therefore consists only of the saidcomposition, which itself consists only of the constituents a, b, c, andd, the sum of which is equal to 100% by weight.

Advantageously, between 90% and 98% of the total length of the tube islocated in the tank.

Advantageously, between 95% and 98% of the total length of the tube islocated in the tank.

More particularly, more than 98% of the total length of the tube islocated in the tank.

The expression “partially annulated” means that the tube has acorrugated tubular shape over part of its length. The annulated part mayform a single portion or more portions of the structure, in which casetwo annulated portions are separated by a smooth portion.

The annulated part(s) allow increasing the deformation and extension ofthe tubular structure, particularly in areas of the tank where smallangles are required.

Advantageously, the tubular structure is annulated over at least 10% ofits length.

Advantageously, the tubular structure is annulated over a proportion ofbetween 10 and more than 90% of its length.

Advantageously, the tubular structure is annulated over a proportion of20 to 90% of its length.

Advantageously, the tubular structure is annulated over a proportion of30 to more than 90% of its length.

Advantageously, the tubular structure is annulated over a proportion of40 to more than 90% of its length.

Advantageously, the tubular structure is annulated over a proportion of50 to more than 90% of its length.

Advantageously, the tubular structure is annulated over a proportion of60 to more than 90% of its length.

Advantageously, the tubular structure is annulated over a proportion of70 to more than 90% of its length.

Advantageously, the tubular structure is annulated over a proportion of80 to more than 90% of its length.

Advantageously, the tubular structure is annulated over a proportion ofmore than 90% of its length.

The expression “being capable of being at least partially submerged insaid tank” means that said structure is either not submerged, regardlessof the fill level of the tank, or that at least 30% of the length ofsaid structure is submerged in the fuel.

It is quite obvious that this proportion depends upon the fuel filllevel in the tank and that the values thus given correspond to a tankcomprising the maximum amount of fuel that it can contain.

Advantageously, at least 40% of the length of said structure issubmerged in the fuel.

Advantageously, at least 50% of the length of said structure issubmerged in the fuel.

Advantageously, at least 60% of the length of said structure issubmerged in the fuel.

Advantageously, at least 70% of the length of said structure issubmerged in the fuel.

Advantageously, at least 80% of the length of said structure issubmerged in the fuel.

In another embodiment, the structure is at least partially within thetank, but is not submerged regardless of the fill level of the tank.

The tubular structure of the invention is intended for transporting fuelinto the tank and therefore does not relate to a tubular structure fortransporting fuel from the tank to the motor or in the motor of thevehicle, even if it is quite obvious that the structure of the inventionhas a small part which is located outside the tank.

Nevertheless, this part will be fixed to a connector making it possibleto connect the tubular structure of the invention to the tubularstructure for transporting fuel from the tank to the motor and thereforecannot be considered as this latter structure for transporting fuel fromthe tank to the motor.

It is quite obvious that when a plasticizer and/or an impact modifierand/or an additive is/are present, a skilled person will vary theproportions of aliphatic polyamide so that the sum a.+b.+c.+d is equalto 100%.

DETAILED DESCRIPTION

Regarding Layer (1)

Layer (1) comprises between 39% and 100% by weight, in particularbetween 41% and 100% by weight, of at least one aliphatic polyamide offormula W/Z.

According to the present application, the term “polyamide,” also denotedPA, covers:

-   -   homopolymers (or homopolyamides),    -   copolymers, or copolyamides, based on different amide units,    -   polyamide alloys, provided that polyamide is the major        constituent.

There is also a category of copolyamides in the broad sense, which,although not preferred, forms part of the scope of the invention. Theseare copolyamides comprising not only amide units (which will be in themajority, and so they are to be considered as copolyamides in the broadsense), but also units of non-amide nature, for example ether units. Thebest known examples are PEBA or polyether-block-amide, and theircopolyamide-ester-ether, copolyamide-ether or copolyamide-estervariants. Among these, mention may be made of PEBA-12 where thepolyamide units are the same as those of PA12, PEBA-612 where thepolyamide units are the same as those of PA612.

The nomenclature used to define the polyamides is described in ISOstandard 1874-1:1992 “Plastiques—Matériaux polyamides (PA) pour moulageand extrusion—Partie 1: Désignation”, in particular on page 3 (Tables 1and 2) and is well known to the person skilled in the art.

In one embodiment, the tubular structure of the invention consists of atleast one layer (1).

The tubular structure can comprise a plurality of identical or differentlayers (1), in particular identical.

In another embodiment, the tubular structure of the invention consistsof a single layer (1) but may comprise other layers.

In yet another embodiment, the structure is monolayer and consists of asingle layer (1).

In the case where the tubular structure is a monolayer structure, saidstructure is therefore in contact with the gasoline both by its externalsurface and by its internal surface.

Regarding the W/Z Repeating Unit

W: Aliphatic Repeating Unit Obtained from the Polycondensation of atLeast One Aminocarboxylic Acid or at Least One Lactam

In a first variant of the invention, the repeating aliphatic unit W isobtained from the polycondensation of at least one C6-C18aminocarboxylic acid, preferably C7-C13 aminocarboxylic acid.

Advantageously, said aminocarboxylic acid comprises from 9 to 12 carbonatoms. It can accordingly be chosen from 9-aminononanoic acid (denoted9), 10-aminodecanoic acid (denoted 10), 11-aminoundecanoic acid (denoted11) and 12-aminododecanoic acid (denoted 12); advantageously theaminocarboxylic acid is 11-aminoundecanoic acid.

In a second variant of the invention, the repeating aliphatic unit W isobtained from the polycondensation of at least one C6-C18 lactam,preferably C7-C13 lactam.

Advantageously, the lactam comprises from 9 to 12 carbon atoms. It canaccordingly be chosen from decanolactam (denoted 10), undecanolactam(denoted 11) and laurolactam or lauryllactam (denoted 12);advantageously, the lactam is lauryllactam.

However, it can absolutely be envisaged to use, for the production ofthis same unit W, a mixture of two or more aminocarboxylic acids, amixture of two or more lactams, but also a mixture of one, two or moreaminocarboxylic acids with one, two or more lactams.

In a more particularly preferred manner, the repeating unit W isobtained from a single aminocarboxylic acid or from a single lactam.

In one embodiment, a repeating unit containing at least 20% repeatingunits obtained from the polycondensation of units derived from anaminocarboxylic acid or a C12 lactam as a raw material is excluded fromthe definition of W.

In another embodiment, a repeating unit containing at least 20% ofrepeating units obtained from the polycondensation of units derived froman aminocarboxylic acid or from a C12 lactam as raw material is excludedfrom the flexible tubular structure of the invention regardless of thenumber of layers of said structure.

In another embodiment, a repeating unit obtained from thepolycondensation of a C12 lactam or aminocarboxylic acid is excludedfrom the definition of W.

In yet another embodiment, a repeating unit obtained from thepolycondensation of a C12 lactam or aminocarboxylic acid as raw materialis excluded from the flexible tubular structure of the inventionregardless of the number of layers of said structure.

W: Aliphatic Repeating Unit X.Y

The aliphatic repeating unit X.Y is a unit obtained from thepolycondensation of at least one linear or branched C6-C18, preferablyC7-C13, aliphatic diamine X or a mixture thereof, and at least oneC6-C18, preferably C7-C13, aliphatic dicarboxylic acid Y.

The molar proportions of diamine and dicarboxylic acid are preferablystoichiometric.

The aliphatic diamine used to obtain this repeating unit X.Y is analiphatic diamine that has a linear main chain comprising from 6 to 18carbon atoms.

This linear main chain can, if necessary, include one or more methyland/or ethyl substituent(s); in the latter configuration, this is calleda “branched aliphatic diamine”. In the case where the main chain doesnot include any substituent, the aliphatic diamine is called a “linearaliphatic diamine.”

Whether or not it includes methyl and/or ethyl substituents on the mainchain, the aliphatic diamine used to obtain this repeating unit X.Ycomprises from 6 to 18 carbon atoms, particularly from 7 to 13 carbonatoms.

When this diamine is a linear aliphatic diamine, it particularlycorresponds to the formula H2N—(CH2)x-NH2 and can be selected forexample from hexanediamine, heptanediamine, octanediamine,nonanediamine, decanediamine, undecanediamine, dodecanediamine,tridecanediamine, tetradecanediamine, hexadecanediamine andoctadecanediamine. The linear aliphatic diamines that have just beencited can all be bio-sourced in the sense of standard ASTM D6866.

When this diamine is a branched aliphatic diamine, it can in particularbe 2-methyl-pentanediamine, 2-methyl-1,8-octanediamine or trimethylene(2,2,4 or 2,4,4) hexanediamine.

The dicarboxylic acid comprises between 6 to 18 carbon atoms,particularly between 7 to 13 carbon atoms.

The aliphatic dicarboxylic acid can be selected from the linear orbranched aliphatic dicarboxylic acids.

When the dicarboxylic acid is aliphatic and linear, it can be selectedfrom adipic acid (6), heptanedioic acid (7), octanedioic acid (8),azelaic acid (9), sebacic acid (10), undecanedioic acid (11),dodecanedioic acid (12), brassylic acid (13), tetradecanedioic acid(14), hexadecanedioic acid (16), octadecanedioic acid (18),octadecanedioic acid (18).

Advantageously, said layer (1) comprises a composition comprising atleast 49% by weight of said at least one aliphatic polyamide.

Advantageously, said layer (1) comprises a composition comprising atleast 50% by weight of said at least one aliphatic polyamide.

Advantageously, said layer (1) comprises a composition comprising atleast 60% by weight of said at least one aliphatic polyamide.

Advantageously, said layer (1) comprises a composition comprising atleast 70% by weight of said at least one aliphatic polyamide.

Advantageously, said layer (1) comprises a composition comprising atleast 80% by weight of said at least one aliphatic polyamide.

Z: Optional Repeating Unit

Z may be any polyamide repeating unit, whether aliphatic,cycloaliphatic, semi-aromatic or aromatic.

Z may be present at up to 30% by weight relative to the total weightW/Z.

Advantageously, Z is present at up to 25% by weight.

Advantageously, Z is present at up to 20% by weight.

Advantageously, Z is present at up to 15% by weight.

Advantageously, Z is present at up to 10% by weight.

Advantageously, Z is present at up to 5% by weight.

Advantageously, Z is equal to 0% by weight.

Regarding the Plasticizer:

The plasticizer is selected particularly from benzene sulfonamidederivatives, such as n-butyl benzene sulfonamide (BBSA); ethyl toluenesulfonamide or N-cyclohexyl toluene sulfonamide; esters ofhydroxy-benzoic acids, such as ethyl-2-hexyl parahydroxybenzoate anddecyl-2-hexyl parahydroxybenzoate; esters or ethers oftetrahydrofurfuryl alcohol, such as oligoethyleneoxytetrahydrofurfurylalcohol; and esters of citric acid or of hydroxy-malonic acid, such asoligoethyleneoxy malonate.

Using a mixture of plasticizers would not be outside the scope of theinvention.

The particularly preferred plasticizer is n-butyl benzene sulfonamide(BBSA).

The plasticizer may be introduced into the polyamide duringpolycondensation or later.

The plasticizer used in the composition is in a proportion by mass of 0to 4%, particularly from 0 to 2%.

Above 4%, the proportion of plasticizer is too high and the proportionof extractables is then too high.

In one embodiment, beyond 2%, the proportion of plasticizer is too highand the proportion of extractables is then too high.

In yet another embodiment, the plasticizer used in the composition is ina proportion by mass of 0.1 to 2%.

Since the tube is partially annulated, this geometry of the tubularstructure provides a certain flexibility and said composition of saidlayer (1) therefore does not necessarily require the presence of aplasticizer.

In an advantageous embodiment, said composition of said layer (1) isdevoid of plasticizer.

Advantageously, the tubular structure is annulated over a proportion ofbetween 10 to more than 90% of its length and said composition of layer(1) is devoid of plasticizer.

Regarding the Impact Modifier

The tubular structure of the invention is located in the tank and, as aresult, the latter is protected from impacts and does not require anyparticular protection against impacts and therefore the impact modifiermay be omitted.

Nevertheless, in order to gain flexibility, the presence of impactmodifier may be useful and/or desirable.

The expression “impact modifier” means a polyolefin based polymer havinga flexural modulus less than 100 MPa measured according to the standardISO 178:2010 (23° C. RH50) and Tg below 0° C. (measured according to thestandard 11357-2:2013 at the level of the inflection point of the DSCthermogram), in particular a polyolefin.

The impact modifier may also be a PEBA (polyether-block-amide) blockpolymer having a flexural modulus<200 MPa.

The polyolefin of the impact modifier can be functionalized ornon-functionalized or be a mixture of at least one functionalizedpolyolefin and/or least one non-functionalized polyolefin.

In particular, a part or all of the polyolefins relates to a functionchosen from the carboxylic acid functions, carboxylic anhydride andepoxide, and is particularly chosen from a copolymer of ethylene andpropylene with an elastomer character (EPR), an ethylene-propylene-dienecopolymer with elastomer character (EPDM) and an ethylene/alkyl(meth)acrylate copolymer, a higher ethylene-alkene copolymer,particularly an ethylene-octene copolymer, an ethylene-alkylacrylate-maleic anhydride terpolymer.

Advantageously, the impact modifier is selected from Fusabond® N493,Fusabond MF416D, a Lotader®, in particular Lotader® 4700, Lotader® 5500,Lotader® 7500 or Lotader® 3410, Exellor® VA1801 or VA1803, Amplify®GR216, Tafmer® MH5020, MH5040, MH7020, MH7010, or a mixture thereof, inwhich case they are in a ratio ranging from 0.1/99.9 to 99.9/0.1,preferably 1/2 to 2/1 when they are in a mixture of two.

By way of example, the impact modifier is selected from the followingmixtures: Fusabond® N493/Lotader®, in particular Fusabond® N493/Lotader®5500 or Fusabond® N493/Lotader® 7500.

The impact modifier may also be a PEBA (polyether-block-amide).

The proportion of impact modifier in said composition of said layer (1)is present between 0 and 20%.

In one embodiment, the impact modifier is present between 3 and 20%.

In another embodiment, the impact modifier is present between 10 and 18%by weight relative to the total weight of the constituents of thecomposition of the layer (1).

In yet another embodiment, the impact modifier is in a proportion byweight of 0% relative to the total weight of the constituents of thecomposition of the layer (1) and is therefore excluded from thecomposition of said layer (1).

Regarding the Additive

The additive or additives d. are selected from carbon black, graphite,graphene, carbon fibers, carbon nanotubes, in particular carbon blackand carbon nanotubes, an antioxidant, a heat stabilizer, a UV absorber,a light stabilizer, a lubricant, an inorganic filler, a fire-proofingagent, a nucleating agent, a dye, reinforcing fibers, a wax and mixturesthereof.

The plasticizers and impact modifiers in the present application areexcluded from the definition of additives.

Said composition of said layer (1) may comprise between 0 and 35% byweight of at least one additive relative to the total weight of thecomposition.

Said layer (1) may therefore be conductive or non-conductive dependingon the presence of carbon black, graphite, graphene, carbon fibers orcarbon nanotubes

Advantageously, one of these additives is an antioxidant.

This antioxidant may be an organic antioxidant or more generally acombination of organic antioxidants, such as a primary antioxidant ofthe phenol type (for example of the type of Ciba's Irganox® 245 or 1098or 1010), a secondary phosphite antioxidant, a phenolic orphosphorus-based antioxidant. Amine antioxidants such as Chemtura'sNaugard® 445 or polyfunctional stabilizers such as Clariant's Nylostab®S-EED can also be used.

This antioxidant may also be a mineral antioxidant, such as acopper-based antioxidant. As an example of such mineral antioxidants,mention may be made of halides and copper acetates, in particularCuI/KI. Secondarily, other metals such as silver can optionally beconsidered, but these are known to be less effective. These compoundscontaining copper are typically associated with alkali metal halides,particularly potassium.

The light stabilizer may be a HALS, which means Hindered Amine LightStabilizer (for example Ciba's Tinuvin® 770).

The UV absorber is, for example, Ciba's Tinuvin® 312.

In accordance with a first variant, the additive is carbon black,particularly in a proportion of between 5 and 32%, in particular between15 and 28%, relative to the total weight of said composition of saidlayer (I). Said additive, which is carbon black, may optionally compriseat least one more additive other than carbon black, graphite, graphene,carbon fibers and carbon nanotubes in a proportion of between 0 and 5%by weight. The proportion of the additive, which is carbon black andoptionally of the other relative additive corresponds to d.

According to a second variant, the additive is carbon nanotubes in aproportion of between 0.5 and 10%, particularly between 2 and 7%, inparticular between 4 to 5% by weight relative to the total weight of thecomposition.

It would not depart from the scope of the invention if, in thesevariants, carbon black were partially replaced by carbon nanotubes orvice versa.

The sum of a.+b.+c.+d. by weight represents 100% of the total weight ofthe composition. As a result, there can be no constituents other thana., b., c., and d. in the composition.

It is quite obvious that whatever the high and low values of the variousconstituents a., b., c. and d. are, the total is 100%. In other words,even if the addition of the high value of one of the constituents a.,b., c. and d. and of the low values of the other constituents mayrepresent more than 100%, it is quite obvious that a person skilled inthe art will vary one or more constituents a., b., c. and d. so that thetotal of the constituents does not exceed 100% by weight.

Whether the tubular structure consists of a single layer or comprisesother layers, as noted hereinbefore, it is located at least partiallyinside the tank, which means that more than 90% of the total length ofthe tube is located in the tank and, as a result, said tubular structureis not a structure for transporting fuel between the tank and the motorof a vehicle, because it can be at least partially submerged in thetank, which results, when it is at least partially submerged, in boththe inner layer of the said tubular structure and the outer layer of thesaid tubular structure being in contact with the fuel, at leastpartially, for the outer layer. In the embodiment wherein the structureis a monolayer structure, the single layer (1) is therefore in contactwith the fuel both on the inner face and on the outer face, at leastpartially for the latter when it is at least partially submerged.

The tubular structure of the invention is also not a tubular structurepresent in the motor.

The polyamides defined hereinbefore in their generalities, whether theyare homopolyamides, copolyamides or alloys, can also be distinguished bytheir number of carbon atoms per nitrogen atom, it being known thatthere are as many nitrogen atoms as amide groups (—CO—NH—).

Tubular structure with an aliphatic polyamide being at least onepolyamide denoted C obtained from the polycondensation of at least oneC6-C 18 lactam or from at least one C6-Cis aminocarboxylic acid.

In one embodiment, the tubular structure defined hereinbefore ischaracterized in that the at least one aliphatic polyamide is at leastone polyamide denoted C obtained from the polycondensation of at leastone C6-C18 lactam, preferably C7-C13 lactam, or from at least one C6-C18aminocarboxylic acid, preferably C7-C13 aminocarboxylic acid, and havingan average number of carbon atoms per nitrogen atom denoted CC rangingfrom 9 to 18, advantageously from 10 to 18.

Throughout the description, the expression “ranging from . . . to . . .” includes the limits and has the same meaning as the expression“between . . . and . . . ”

It is quite obvious that to obtain an average number of carbon atoms pernitrogen atom denoted CC ranging from 9 to 18 with a polyamide denoted Cobtained from the polycondensation of at least one C7 or C8 lactam, orof at least one C7 or C8 aminocarboxylic acid, said polyamide denoted Cmust be a copolyamide or a polyamide mixture whose second unit has anaverage number of carbon atoms per nitrogen atom denoted CC higher than9 depending on the molar proportion of said second unit.

Advantageously, said at least one aliphatic polyamide is a singlepolyamide denoted C obtained from the polycondensation of at least oneC6-C18 lactam, preferably C7-C13 lactam, or of at least one C6-C18aminocarboxylic acid, preferably C7-C13 aminocarboxylic acid, and havingan average number of carbon atoms per nitrogen atom denoted CC rangingfrom 9 to 18, advantageously from 10 to 18.

In another embodiment, said constituent a. of said composition furthercomprises another polyamide selected from:

-   -   at least one polyamide denoted A having an average number of        carbon atoms per nitrogen atom denoted CA ranging from 4 to 8.5,        advantageously from 4 to 7;    -   at least one polyamide denoted B having a melting temperature        higher than or equal to 180° C. and an average number of carbon        atoms per nitrogen atom denoted CB ranging from 7 to 10,        advantageously from 7.5 to 9.5;    -   or a mixture thereof,    -   the weighted average mass of the melting enthalpies of the        polyamides being higher than 25 J/g (DSC),    -   the average number of carbon atoms per nitrogen atom of the        polyamides A, B and C further satisfying the following strict        inequation: CA<CB<CC.

The polyamide denoted A and the polyamide denoted B, said polyamidedenoted B having a melting temperature higher than or equal to 180° C.,are polyamides obtained either from the polycondensation of at least onelactam, or of at least one aminocarboxylic acid and having respectivelyan average number of carbon atoms per nitrogen atom denoted CA rangingfrom 4 to 8.5, advantageously from 4 to 7, and an average number ofcarbon atoms per nitrogen atom denoted CB ranging from 7 to 10,advantageously from 7.5 to 9.5, but may also be a PA X′Y′ obtained fromthe polycondensation of a linear or branched aliphatic diamine X′,provided that the average number of carbon atoms per nitrogen atom isrespected for each of the polyamides A and B.

Advantageously, the difference between the average numbers of carbonatoms per nitrogen atom (CB−CA) and/or (CC−CB) ranges from 1 to 4, andpreferably from 2 to 3.

The melting enthalpy and the melting temperature of the polyamides isdetermined in accordance with ISO 11357-3: 2013.

The composition of said layer (1) may therefore comprise a polyamidedenoted C and a polyamide denoted A, or a polyamide denoted C and apolyamide denoted B, or alternatively a polyamide denoted C, a polyamidedenoted A and a polyamide denoted B.

The proportion by mass of the various polyamides in the hereinbeforecompositions is variable, which means that one of the polyamides denotedA, B or C is in the majority relative to the sum C+A, C+B or C+A+B.

In a first variant, said constituent a. of said composition furthercomprises at least one polyamide denoted A having an average number ofcarbon atoms per nitrogen atom denoted CA ranging from 4 to 8.5,advantageously from 4 to 7.

Advantageously, the melting temperature of polyamide A is higher than orequal to 210° C.

In a second variant, said constituent a. of said composition furthercomprises at least one polyamide denoted B having a melting temperaturehigher than or equal to 180° C. and an average number of carbon atomsper nitrogen atom denoted CB ranging from 7 to 10, advantageously from7.5 to 9.5.

Advantageously, the melting temperature of polyamide B is less than orequal to 200° C.

In a third variant, said constituent a. of said composition furthercomprises at least one polyamide denoted A having an average number ofcarbon atoms per nitrogen atom denoted CA ranging from 4 to 8.5,advantageously from 4 to 7, and at least one polyamide denoted B havinga melting temperature higher than or equal to 180° C., and an averagenumber of carbon atoms per nitrogen atom denoted CB ranging from 7 to10, advantageously from 7.5 to 9.5.

Advantageously, the melting temperature of polyamide A is higher than orequal to 210° C., and/or the melting temperature of polyamide B is lessthan or equal to 200° C.

Advantageously, said composition of the three variants definedhereinbefore comprises between 34 and 84% by weight of aliphaticpolyamide C relative to the total weight of the polyamides presentwithin said composition, preferably between 50 and 80%.

More advantageously, said composition of the three variants definedhereinbefore comprises between 60 and 80% by weight of aliphaticpolyamide C relative to the total weight of the polyamides presentwithin said composition.

More advantageously, said composition of the three variants definedhereinbefore comprises between 70 and 80% by weight of aliphaticpolyamide C relative to the total weight of the polyamides presentwithin said composition.

When said aliphatic polyamide of the tubular structure is, at least, apolyamide denoted C obtained from the polycondensation of at least oneC6-C18 lactam, preferably C7-C13 lactam, or of at least one C6-C18aminocarboxylic acid, preferably C7-C13 aminocarboxylic acid, then saidpolyamide C is advantageously selected from PA11 and PA12,advantageously PA11.

In the first variant, said polyamide C is advantageously selected fromPA11 and PA12, advantageously PA11 and polyamide A is selected from PA6,PA46 and PA66.

In the second variant, said polyamide C is advantageously selected fromPA11 and PA12, advantageously PA11 and polyamide B is selected fromPA610 and PA612.

In the third variant, said polyamide C is advantageously selected fromPA11 and PA12, advantageously PA11, polyamide B is selected from PA610,and PA612 and polyamide A is selected from PA6, PA46 and PA66.

Advantageously, each of the polyamides A, B and C has a melting enthalpyhigher than 25 J/g (DSC).

In one embodiment, said tubular structure is characterized in that W insaid aliphatic polyamide of formula W/Z is at least one aliphaticrepeating unit XY, which is a polyamide denoted B′ having a meltingtemperature higher than or equal to 180° C., and an average number ofcarbon atoms per nitrogen atom denoted CB′ ranging from 7 to 10,advantageously from 7.5 to 9.5, or a polyamide denoted C′ having anaverage number of carbon atoms per nitrogen atom denoted CC′ rangingfrom 9 to 18, advantageously from 10 to 18.

In another embodiment, the tubular structure defined hereinbefore ischaracterized in that W in said at least one aliphatic polyamide offormula W/Z is an aliphatic repeating unit XY, which is a polyamidedenoted B′ having a melting temperature higher than or equal to 180° C.,and an average number of carbon atoms per nitrogen atom denoted CB′ranging from 7 to 10, advantageously from 7.5 to 9.5, or a polyamidedenoted C′ having an average number of carbon atoms per nitrogen atomdenoted CC′ ranging from 9 to 18, advantageously from 10 to 18.

The repeating units resulting from the polycondensation of lactamsand/or aminocarboxylic acid are therefore excluded from the polyamidesdenoted B′ or denoted C′.

Advantageously, said aliphatic polyamide is a single polyamide denotedB′ or a single polyamide denoted C′.

In one embodiment, said constituent a. of said composition consisting ofat least one aliphatic polyamide denoted B′ or denoted C′ furthercomprises another polyamide selected from:

-   -   at least one polyamide denoted A having an average number of        carbon atoms per nitrogen atom denoted CA ranging from 4 to 8.5,        advantageously from 4 to 7;    -   at least one polyamide denoted B″ having a melting temperature        higher than or equal to 180° C. and an average number of carbon        atoms per nitrogen atom denoted CB ranging from 7 to 10,        advantageously from 7.5 to 9.5, when said aliphatic polyamide is        C′,    -   at least one polyamide denoted C″ having an average number of        carbon atoms per nitrogen atom denoted CC″ ranging from 9 to 18,        advantageously from 10 to 18, when said aliphatic polyamide is        B′;    -   or a mixture thereof,    -   the weighted average mass of the melting enthalpies of the        polyamides being higher than 25 J/g (DSC),    -   the average number of carbon atoms per nitrogen atom in units A,        B′, B″, C′ and C″ further satisfying the following strict        inequation: CA<CB′ or CB″<CC′ or CC″.

The polyamide denoted A is a polyamide obtained as describedhereinbefore, the polyamide denoted B″ is a polyamide obtained asdescribed hereinbefore for polyamide B and the polyamide denoted C″ is apolyamide obtained as described hereinbefore for polyamide C, providedthat the average number of carbon atoms per nitrogen atom is respectedfor each of the polyamides A, B″ and C″.

Advantageously, the difference between the average numbers of carbonatoms per nitrogen atom (CB′—CA) and/or (CC′—CB″) and/or (CC″—CB″)ranges from 1 to 4, and preferably from 2 to 3.

The composition of said layer (1) may therefore comprise:

-   -   a polyamide denoted B′ and a polyamide denoted A,    -   a polyamide denoted B′ and a polyamide denoted C″,    -   a polyamide denoted B′, a polyamide denoted A and a polyamide        denoted C″,    -   a polyamide denoted C′ and a polyamide denoted A,    -   a polyamide denoted C′ and a polyamide denoted B″,    -   a polyamide denoted C′, a polyamide denoted A and a polyamide        denoted B″.

The proportion by mass of the various polyamides in the hereinbeforecompositions is variable, which means that one of the polyamides denotedA, B′ or C″ is the majority relative to the total of the polyamidesA+B′+C″ or that one of the polyamides denoted A, B″ or C′ is themajority relative to the total of the polyamides A+B″+C′ present in thecomposition.

In a first variant, said at least one aliphatic polyamide denoted B′further comprises at least one polyamide denoted A having an averagenumber of carbon atoms per nitrogen atom denoted CA ranging from 4 to8.5, advantageously from 4 to 7.

In a second variant, said at least one aliphatic polyamide denoted B′further comprises at least one polyamide denoted C″ having an averagenumber of carbon atoms per nitrogen atom denoted CC″ ranging from 9 to18, advantageously from 10 to 18.

In a third variant, said at least one aliphatic polyamide denoted B′further comprises at least one polyamide denoted A having an averagenumber of carbon atoms per nitrogen atom denoted CA ranging from 4 to8.5, advantageously from 4 to 7, and at least one polyamide denoted C″having an average number of carbon atoms per nitrogen atom denoted CC″ranging from 9 to 18, advantageously from 10 to 18.

In a fourth variant, said at least one aliphatic polyamide denoted C′further comprises at least one polyamide denoted A having an averagenumber of carbon atoms per nitrogen atom denoted CA ranging from 4 to8.5, advantageously from 4 to 7.

In a fifth variant, said at least one aliphatic polyamide denoted C′further comprises at least one polyamide denoted B″ having a meltingtemperature higher than or equal to 180° C. and an average number ofcarbon atoms per nitrogen atom denoted CB′ ranging from 7 to 10,advantageously from 7.5 to 9.5.

In a sixth variant, said at least one aliphatic polyamide denoted C′further comprises at least one polyamide denoted A having an averagenumber of carbon atoms per nitrogen atom denoted CA ranging from 4 to8.5, advantageously from 4 to 7, and at least one polyamide denoted B″having a melting temperature higher than or equal to 180° C., and anaverage number of carbon atoms per nitrogen atom denoted CB″ rangingfrom 7 to 10, advantageously from 7.5 to 9.5.

Advantageously, the melting temperature of polyamide A is higher than orequal to 210° C., and/or the melting temperature of polyamide C″ is lessthan or equal to 200° C., and/or the temperature of polyamide B″ ishigher than or equal to 180° C.

Advantageously, said composition of three of the six variants definedhereinbefore comprises between 34 and 84% by weight of aliphaticpolyamide B′ relative to the total weight of the polyamides presentwithin said composition, preferably between 50 and 80%.

More advantageously, said composition of three of the six variantsdefined hereinbefore comprises between 60 and 80% by weight of aliphaticpolyamide B′ relative to the total weight of the polyamides presentwithin said composition.

More advantageously, said composition of three of the six variantsdefined hereinbefore comprises between 70 and 80% by weight of aliphaticpolyamide B′ relative to the total weight of the polyamides presentwithin said composition.

Advantageously, said composition of three of the six variants definedhereinbefore comprises between 34 and 84% by weight of aliphaticpolyamide C′ relative to the total weight of the polyamides presentwithin said composition, preferably between 50 and 80%.

More advantageously, said composition of three of the six variantsdefined hereinbefore comprises between 60 and 80% by weight of aliphaticpolyamide C′ relative to the total weight of the polyamides presentwithin said composition.

More advantageously, said composition of three of the six variantsdefined hereinbefore comprises between 70 and 80% by weight of aliphaticpolyamide C′ relative to the total weight of the polyamides presentwithin said composition.

When the said at least one aliphatic polyamide of the tubular structureis an aliphatic repeating unit, which is a polyamide denoted B′, thenthe said polyamide B′ is advantageously selected from PA610 and PA612,advantageously PA610.

When the said at least one aliphatic polyamide of the tubular structureis an aliphatic repeating unit, which is a polyamide denoted C′, thenthe said polyamide C′ is advantageously selected from PA1012, PA618 andPA1010.

In the first variant, said polyamide B′ is advantageously selected fromPA610 and PA612, advantageously PA610 and polyamide A is selected fromPA6, PA46 and PA66.

In the second variant, said polyamide B′ is advantageously selected fromPA610 and PA612, advantageously PA610 and polyamide C″ is selected fromPA11, PA12, PA1012, PA618 and PA1010.

In the third variant, said polyamide B′ is advantageously selected fromPA610 and PA612, advantageously PA610, polyamide A is selected from PA6,PA46 and PA66 and polyamide C″ is selected from PA11, PA12, PA1012,PA618 and PA1010.

In the fourth variant, said polyamide C′ is advantageously selected fromPA1012, PA618 and PA1010, and polyamide A is selected from PA6, PA46 andPA66.

In the fifth variant, said polyamide C′ is advantageously selected fromPA1012, PA618 and PA1010, and polyamide B″ is advantageously selectedfrom PA610 and PA612, advantageously PA610.

In the sixth variant, said polyamide C′ is selected from PA1012, PA618and PA1010, polyamide A is selected from PA6, PA46 and PA66, andpolyamide B″ is advantageously selected from PA610 and PA612,advantageously PA610.

Advantageously, each of the polyamides A, B′, B″, C′ and C″ has amelting enthalpy higher than 25 J/g (DSC).

Advantageously, when the structure consists of a single layer, which isthe layer (1), the composition of said layer (1) is devoid of anadditive selected from carbon black, graphite, graphene, carbon fibersand carbon nanotubes.

In this embodiment, the tubular structure is therefore non-conductiveand devoid of any other layer.

All the characteristics of the various constituents a., b., c. and d.defined hereinbefore are valid for this particular embodiment with theexception of the additives selected from carbon black, graphite,graphene, carbon fibers and carbon nanotubes.

Advantageously, when the tubular structure is a monolayer structure, thethickness of said layer (1) is at least 600 μm.

Advantageously, said monolayer tubular structure devoid of additiveselected from carbon black, graphite, graphene, carbon fibers and carbonnanotubes is also devoid of plasticizer.

Tubular Structure in which the Additive is at Least Carbon Black

In one embodiment, said tubular structure, defined hereinbefore,comprises an additive in the layer (1) which is at least carbon black.

Other additives may be present in said layer (1), but they are thennon-conductive. The tubular structure may be monolayer or multilayer.

Advantageously, it is multilayer.

In a first variant, said tubular structure defined hereinbefore ischaracterized in that said composition of said layer (1) comprises:

-   -   a. between 39% and 95% by weight, in particular between 41% to        85% by weight of at least one aliphatic polyamide,    -   b. between 0% and 4% by weight, preferably between 0 and 2% of a        plasticizer,    -   c. between 0% and 20% by weight of at least one impact modifier,    -   d. between 5% and 32%, in particular between 15 and 28% by        weight of an additive, which is carbon black, and    -   between 0 and 5% by weight of at least one additive other than        carbon black, graphite, graphene, carbon fibers and carbon        nanotubes,    -   the sum a.+b.+c.+d. being equal to 100%.

The additives, plasticizers, impact modifiers are as definedhereinbefore.

In one embodiment, said tubular structure defined hereinbefore ischaracterized in that said composition of said layer (1) consists of:

-   -   a. between 39% and 95% by weight, in particular between 41% to        85% by weight of at least one aliphatic polyamide,    -   b. between 0% and 4% by weight, preferably between 0 and 2% of a        plasticizer,    -   c. between 0% and 20% by weight of at least one impact modifier,    -   d. between 5% and 32%, in particular between 15 and 28% by        weight of an additive, which is carbon black, and    -   between 0 and 5% by weight of at least one additive other than        carbon black, graphite, graphene, carbon fibers and carbon        nanotubes,    -   the sum a.+b.+c.+d. being equal to 100% of the total weight of        the composition.

In a second variant, said tubular structure defined hereinbefore ischaracterized in that said composition of said layer (1) comprises:

-   -   a. between 39% and 85% by weight, in particular between 41% and        75% by weight of at least one aliphatic polyamide,    -   b. between 0% and 4% by weight, preferably between 0 and 2% of a        plasticizer,    -   c. between 10% and 18% of at least one impact modifier,    -   d. between 5% and 32%, in particular between 15 and 28% by        weight of an additive, which is carbon black, and    -   between 0 and 5% by weight of at least one additive other than        carbon black, graphite, graphene, carbon fibers and carbon        nanotubes,    -   the sum a.+b.+c.+d. being equal to 100%.

In one embodiment, said tubular structure defined hereinbefore ischaracterized in that said composition of said layer (1) consists of:

-   -   a. between 39% and 85% by weight, in particular between 41% and        75% by weight of at least one aliphatic polyamide,    -   b. between 0% and 4% by weight, preferably between 0 and 2% of a        plasticizer,    -   c. between 10% and 18% of at least one impact modifier,    -   d. between 5% and 32%, in particular between 15 and 28% by        weight of an additive, which is carbon black, and    -   between 0 and 5% by weight of at least one additive other than        carbon black, graphite, graphene, carbon fibers and carbon        nanotubes,    -   the sum a.+b.+c.+d. being equal to 100% of the total weight of        the composition.        Tubular Structure in which the Additive is at Least Carbon        Nanotubes

In one embodiment, said tubular structure, defined hereinbefore,comprises an additive in the layer (1) which is at least carbonnanotubes.

Other additives may be present in said layer (1), but they are thennon-conductive.

Said tubular structure may be monolayer or multilayer.

In a first variant, said tubular structure defined hereinbefore ischaracterized in that said composition of said layer (1) comprises:

-   -   a. between 70% and 99.5% by weight, particularly between 80% and        98% by weight, in particular 80% and 96% by weight of at least        one aliphatic polyamide,    -   b. between 0% and 4% by weight, preferably between 0 and 2% of a        plasticizer,    -   c. between 0% and 20% of at least one impact modifier,    -   d. between 0.5% and 10%, preferably between 2 and 7%, in        particular between 4 and 5% by weight of an additive which is        carbon nanotubes, and    -   between 0 and 19%, preferably between 0 and 22%, in particular        between 0 and 24% by weight of at least one additive other than        carbon black, graphite, graphene, carbon fibers and carbon        nanotubes,    -   the sum a.+b.+c.+d. being equal to 100%.

In one embodiment, said tubular structure defined hereinbefore ischaracterized in that said composition of said layer (1) consists of:

-   -   a. between 70% and 99.5% by weight, particularly between 80% and        98% by weight, in particular 80% and 96% by weight of at least        one aliphatic polyamide,    -   b. between 0% and 4% by weight, preferably between 0 and 2% of a        plasticizer,    -   c. between 0% and 20% of at least one impact modifier,    -   d. between 0.5% and 10%, preferably between 2 and 7%, in        particular between 4 and 5% by weight of an additive which is        carbon nanotubes, and    -   between 0 and 19%, preferably between 0 and 22%, in particular        between 0 and 24% by weight of at least one additive other than        carbon black, graphite, graphene, carbon fibers and carbon        nanotubes,    -   the sum a.+b.+c.+d. being equal to 100% of the total weight of        the composition.

In a second variant, said tubular structure defined hereinbefore ischaracterized in that said composition of said layer (1) comprises

-   -   a. between 70% and 89.5% by weight, particularly between 80% and        88% by weight, in particular 80% and 86% by weight of at least        one aliphatic polyamide,    -   b. between 0% and 4% by weight, preferably between 0 and 2% of a        plasticizer,    -   c. between 10% and 18% of at least one impact modifier,    -   d. between 0.5% and 10%, preferably between 2 and 7%, in        particular between 4 and 5% by weight of an additive which is        carbon nanotubes, and    -   between 0 and 19%, preferably between 0 and 22%, in particular        between 0 and 24% by weight of at least one additive other than        carbon black, graphite, graphene, carbon fibers and carbon        nanotubes,    -   the sum a.+b.+c.+d. being equal to 100%.

In one embodiment, said tubular structure defined hereinbefore ischaracterized in that said composition of said layer (1) consists of:

-   -   a. between 70% and 89.5% by weight, particularly between 80% and        88% by weight, in particular 80% and 86% by weight of at least        one aliphatic polyamide,    -   b. between 0% and 4% by weight, preferably between 0 and 2% of a        plasticizer,    -   c. between 10% and 18% of at least one impact modifier,    -   d. between 0.5% and 10%, preferably between 2 and 7%, in        particular between 4 and 5% by weight of an additive which is        carbon nanotubes, and    -   between 0 and 19%, preferably between 0 and 22%, in particular        between 0 and 24% by weight of at least one additive other than        carbon black, graphite, graphene, carbon fibers and carbon        nanotubes,    -   the sum a.+b.+c.+d. being equal to 100% of the total weight of        the composition.

Advantageously, the layer (1) of one of the tubular structures definedhereinbefore is devoid of plasticizer.

Tubular Structure Comprising at Least One Layer (1) and at Least OneLayer (2)

In another embodiment, the hereinbefore defined tubular structure ischaracterized in that it comprises at least one second layer (2) that isconductive or non-conductive, in particular conductive, said layer (1)being located above or below said layer (2).

The expression “above” means outside the tubular structure, said layer(1) therefore being the outer layer and said layer (2) being the innerlayer.

The expression “below” means inside the tubular structure, said layer(1) therefore being the inner layer and said layer (2) being the outerlayer.

The tubular structure then corresponds to a multilayer structure (MLT).

Advantageously, said layer (1) is located above said layer (2).

Advantageously, the thickness of the layer (1) in the MLT structure isbetween about 600 μm and about 950 μm.

Advantageously, the thickness of said layer (2) in the MLT structurerepresents less than 25% of the total thickness of the MLT.

Advantageously, when said second layer (2) is conductive, its thicknessis between 50 and 200 μm.

Advantageously, said tubular structure comprising at least one secondlayer (2) is characterized in that said second layer (2) comprises atleast one aliphatic polyamide or fluorinated materials such as PVDF orfunctionalized fluorinated materials such as the functionalizedethylene-tetrafluoroethylene (ETFE) copolymer, the functionalizedethylene-tetrafluoroethylene-hexafluoropropylene (EFEP) copolymer, atetrafluoroethylene-perfluoro (alkylvinylether)-chlorotrifluoroethylene(CPT) copolymer.

All the technical characteristics detailed hereinbefore for the layer(1) of the tubular structure are valid for this embodiment in which atleast one layer (1) and at least one layer (2) are present.

Said at least one second layer (2) is conductive or non-conductive,which means that it may contain additives selected from carbon black,graphite, graphene, carbon fibers and carbon nanotubes and said layer(1) is conductive or non-conductive.

In a first variant, said at least one second layer (2) is devoid ofplasticizer.

In a second variant, said at least one second layer (2) is conductiveand comprises between 0.5 and 10%, preferably between 2% and 7%, inparticular between 4 and 5% by weight of an additive, which is carbonnanotubes, or between 5% and 24%, in particular between 15 and 24% byweight of an additive, which is carbon black, relative to the totalweight of the composition of said layer (2).

In a third variant, said at least one second layer (2) is conductive andcomprises between 0.5 and 10%, preferably between 2% and 7%, inparticular between 4 and 5% by weight of an additive, which is carbonnanotubes, or between 5% and 24%, in particular between 15 and 24% byweight of an additive, which is carbon black, relative to the totalweight of the composition of said layer (2) and is devoid ofplasticizer.

In a fourth variant, said at least one second layer (2) is conductiveand comprises between 0.5 and 10%, preferably between 2% and 7%, inparticular between 4 and 5% by weight of an additive, which is carbonnanotubes, or between 5% and 24%, in particular between 15 and 24% byweight of an additive, which is carbon black, relative to the totalweight of the composition of said layer (2) and said layer (1) isnon-conductive.

In a fifth variant, said at least one second layer (2) is conductive andcomprises between 0.5 and 10%, preferably between 2% and 7%, inparticular between 4 and 5% by weight of an additive, which is carbonnanotubes, or between 5% and 24%, in particular between 15 and 24% byweight of an additive, which is carbon black, relative to the totalweight of the composition of said layer (2), said layer (2) being devoidof plasticizer and said layer (1) is non-conductive.

In a sixth variant, said at least one second layer (2) is conductive andcomprises between 0.5 and 10%, preferably between 2% and 7%, inparticular between 4 and 5% by weight of an additive, which is carbonnanotubes, or between 5% and 24%, in particular between 15 and 24% byweight of an additive, which is carbon black, relative to the totalweight of the composition of said layer (2), said layer (2) being devoidof plasticizer and said layer (1) is non-conductive and said layer (1)is devoid of plasticizer.

In another embodiment, the hereinbefore defined tubular structure ischaracterized in that it comprises two conductive or non-conductivelayers (2), in particular conductive, said layer (1) being locatedbetween the said two layers (2).

The expression “barrier layer” means a layer of low permeability tofuels, particularly to alcoholic gasolines, and which consequentlyallows very little passage of fuel, particularly alcoholic gasolines,into the atmosphere.

In particular, the expression “barrier layer” means that the proportionof fuel, in particular of alcohol-based gasoline emitted to theatmosphere is less than 20 g·mm/m2 day as determined with a CE10 fuel at60° C.

The fuel permeability, particularly gasoline permeability, are measuredat 60° C. according to a gravimetric method with CE10:isooctane/toluene/ethanol=45/45/10 vol % and CE85:isooctane/toluene/ethanol=7.5/7.5/85 vol % on plates made of a polymermaterial. The instant permeability is zero during the induction period,then it increases progressively up to a value at equilibrium thatcorresponds to the permeability value in the permanent regime. Thisvalue obtained in the permanent regime is considered as being thematerial's permeability.

This bather property is essential for tubes in contact with theatmosphere.

In the case of the tubular structures of the invention, the latter beingsubmerged in the fuel, a bather layer is not necessary. As a result,advantageously,

In one variant, the tubular structure defined hereinbefore comprising atleast one second layer (2) is devoid of a barrier layer and the tubularstructure then consists only of aliphatic polyamides.

Said aliphatic polyamide of the layer (2) is as defined hereinbefore andmay comprise the same additives, impact modifier, plasticizer as thepolyamide of the layer (1) and this in ranges of proportions identicalto those of the layer (1).

Said fluorinated material may comprise additives similar to those of thepolyamide of the layer (1) and this in ranges of proportions identicalto those of the layer (1). Advantageously, said second layer (2)comprises a composition comprising at least one aliphatic polyamide, asdefined for said layer (1).

In another embodiment, the tubular structure defined hereinbefore andcomprising at least one second layer (2) also comprises a third layer(2′), identical to or different from the second layer (2).

Advantageously, said layer (2′) comprises a composition comprising apolyamide as that defined for said layer (2).

Advantageously, said layers (2) and (2′) are conductive and the layer(1) is non-conductive.

Advantageously, when the tubular structure comprises at least one layer(1) and at least one layer (2), the thickness of said layer (1) isbetween 60% and 95% of the total thickness of the tube.

According to another aspect, the present invention relates to the use ofa tubular structure as defined hereinbefore, for transporting fuels intothe tank, in particular for transporting gasoline into the tank.

All the characteristics defined hereinbefore for the tubular structureare valid for this use.

According to another aspect, the present invention relates to the use ofa tubular structure as defined hereinbefore, in order to satisfy anextractable test, said test particularly consisting of filling saidmultilayer tubular structure MLT with FAM-B alcohol-based gasoline andheating the assembly at 60° C. for 96 hours, then emptying it byfiltering it into a beaker, then allowing the filtrate from the beakerto evaporate at ambient temperature and finally weighing this residue,the proportion of which must be less than or equal to approximately 10g/m2 of internal tube surface, preferably less than or equal to 6 g/m2.

According to another aspect, the present invention relates to a methodfor measuring the extractables of a tubular structure, as definedhereinbefore, comprising the following steps:

-   -   1) filling said tubular structure with FAM-B alcohol-based        gasoline,    -   2) heating said tubular structure submerged in said gasoline at        60° C. for 96 hours,    -   3) emptying with simultaneous filtration into a beaker,    -   4) evaporating the filtrate from the beaker at ambient        temperature    -   5) weighing the residue after evaporation, the proportion of        which must be less than or equal to about 6 g/m2 of internal        tube surface.

Examples

The invention will now be described in more detail with the aid of thefollowing non-limiting examples.

The following structures were prepared by extrusion:

The multi-layer tubes are manufactured by co-extrusion. An industrialMcNeil multilayer extrusion line is used, equipped with 5 extruders,connected to a multilayer extrusion head with spiral mandrels.

The screws used are extrusion monoscrews having screw profiles adaptedto polyamides. In addition to the 5 extruders and the multilayerextrusion head, the extrusion line comprises:

-   -   a die-punch assembly, located at the end of the coextrusion        head; the internal diameter of the die and the external diameter        of the punch are selected according to the structure to be        produced and the materials of which it is composed, as well as        the dimensions of the tube and the line speed;    -   a vacuum tank with an adjustable vacuum level. In this tank        water circulates generally maintained at 20° C., in which a        gauge is submerged making it possible to shape the tube to its        final dimensions. The diameter of the gauge is adapted to the        dimensions of the tube to be produced, typically from 8.5 to 10        mm for a tube with an external diameter of 8 mm and a thickness        of 1 mm;    -   a succession of cooling tanks in which water is maintained at        around 20° C., allowing the tube to be cooled along the path        from the head to the drawing bench;    -   a diameter meter;    -   a drawing bench.

The configuration with 5 extruders is used to produce tubes ranging from2 layers to 5 layers. In the case of structures whose number of layersis less than 5, several extruders are then fed with the same material.

In the case of structures comprising 6 layers, an additional extruder isconnected and a spiral mandrel is added to the existing head, in orderto make the inner layer, in contact with the fluid.

Before the tests, in order to ensure the best properties for the tubeand good extrusion quality, it is verified that the extruded materialshave a residual moisture content before extrusion of less than 0.08%.Otherwise, an additional step of drying the material before the tests,generally in a vacuum dryer, is carried out overnight at 80° C.

The tubes, which satisfy the characteristics disclosed in the presentpatent application, were removed, after stabilization of the extrusionparameters, the dimensions of the tubes in question no longer changingover time. The diameter is controlled by a laser diameter meterinstalled at the end of the line.

Generally, the line speed is typically 20 m/min. It generally rangesfrom 5 to 100 m/min.

The screw speed of the extruders depends on the thickness of the layerand on the diameter of the screw, as is known to those skilled in theart.

In general, the temperatures of the extruders and of the tools (head andconnector) must be adjusted so as to be sufficiently higher than themelting temperature of the compositions in question, so that they remainin the molten state, thus preventing them from solidifying and jammingthe machine.

The tubular structures were tested on different parameters (Table I).

All the layer thicknesses are expressed in μm.

The amount of extractables, the bursting pressure properties and theflexibility properties were determined.

Extract- Bursting Flexi- Examples and ables pressure bility contrastingexamples (3) (1) (2) Contrasting example c1: >50 + +++++ PA12-TL 1000 μmthickness monolayer Contrasting example c2: >40 ++ ++++++ PA11-TL 1000μm thickness monolayer Contrasting example c3: >40 ++++ ++++ PA610-TL1000 μm thickness monolayer Contrasting example c4: >40 +++ ++++PA612-TL 1000 μm thickness monolayer Contrasting example c5 >40 ++++++++ (multilayer): PA12-TL//PA612-TL//PA12-TL thicknesses: 100//800/100μm Example 1: <4 ++ +++ PA11-NoPlast 1000 μm thickness monolayer Example2: <4 ++++ ++ PA610-NoPlast 1000 μm thickness monolayer Example 3: <4+++ ++ PA612-NoPlast 1000 μm thickness monolayer Example 4: <4 ++++ +PA612-NoPlast-B 1000 μm thickness monolayer Example 5 (multilayer): <5+++ ++ PA12-NoPlast//PA612-NoPlast thicknesses: 100//900 μm Example 6(multilayer): <5 +++ +++ PA12-NoPlast//PA612-NoPlast// PA12-NoPlastthicknesses: 100//800//100 μm Example 7 (multilayer): <4 +++ +++PA11-NoPlast//PA612-NoPlast// PA11-NoPlast thicknesses: 100//800//100 μmExample 8 (multilayer): <4 ++++ +++ PA11-NoPlast//PA610-NoPlast//PA11-NoPlast thicknesses: 100//800//100 μm Example 9 (multilayer): <4++++ ++ PA11-NoPlast// PA610-NoPlast// PA11cond-NoPlast thicknesses:100//800//100 μm Example 10 (multilayer): <2 ++++ ++EFEPc//PA610-NoPlast//EFEPc thicknesses: 100//800//100 μm Example 11(multilayer): <2 ++ ++ EFEPc//PA11-NoPlast// EFEPc thicknesses:100//800//100 μm Example 12 (multilayer): <5 ++++ ++PA12-NoPlast//Binder- NoPlast//PA6-NoPlast thicknesses: 100//100//800 μm+++ +++ Example 13 (multilayer): <5 PA12-NoPlast//Binder-NoPlast//PA6-NoPlast//Binder- NoPlast// PA12-NoPlast thicknesses:100//100//600//100//100 μm Example 14 (multilayer): <6 ++++ +++PA11-TL//PA610-NoPlast thicknesses: 100//900 μm Example 15: <9 ++ +++++PA11-P 1000 μm thickness monolayer (1) Bursting pressure is the burstingpressure (according to DIN 53758) after at least 96 hours with FAM-Bbiogas inside, so a value high enought to withstand the pressure issought. The higher the number of “+”, the better the bursting pressure.(2) Flexibility and flexural modulus (according to ISO 178) on the tubewhen conditioned at 23° C. in RH50. The lower the modulus, the higherthe flexibility, which is favorable for mounting the tube. The higherthe number of “+”, the better the flexibility. (3) Extractables. Thetest consisting of a tube filled with FAM-B alcohol-based gasoline at60° C. for 96 hours, then emptied and filtered into a beaker which isthen allowed to evaporate and the residue of which is weighted, thelatter preferably being less than or equal to 6 g/m2 (of internalsurface of the tube). The FAM B alcohol-based gasoline is disclosed instandard DIN 51604-1: 1982, DIN 51604-2: 1984 and DIN 51604-3: 1984. Inbrief, FAM A alcohol-based gasoline is first prepared with a mixture of50% toluene, 30% isooctane, 15% di-isobutylene and 5% ethanol and thenFAM B.

Compositions

-   -   PA12-TL denotes a polyamide 12-based composition, containing 6%        plasticizer, 6% EPR1, and 1.2% organic stabilizers. The melting        temperature of this composition is 175° C.    -   PA11-TL denotes a polyamide 11-based composition, containing 5%        plasticizer, 6% impact modifier of the ethylene/ethyl        acrylate/anhydride type in a mass ratio of 68.5/30/1.5 (MFI 6 at        190° C. under 2.16 kg), and 1.2% organic stabilizers. The        melting temperature of this composition is 185° C.    -   PA12-NoPlast=PA12-TL without the plasticizer (the latter is        replaced by PA12)    -   PA11-NoPlast=PA11-TL without the plasticizer (the latter is        replaced by PA11)    -   PA610-TL=PA610+12% EPR1 impact modifier+organic stabilizer+10%        plasticizer    -   PA610-NoPlast=PA610-TL without the plasticizer (the latter is        replaced by PA610)    -   PA612-TL=PA612+12% EPR1 impact modifier+organic stabilizer+9%        plasticizer    -   PA612-NoPlast=PA612-TL without the plasticizer (the latter is        replaced by PA612)    -   PA612-NoPlast-B=PA612-TL without the plasticizer or EPR1 (these        are replaced by PA612)    -   PA11cond-noplast=PAU of Mn 15000+9% EPR1+26% Ensaco type carbon        black 250 G    -   PA6-NoPlast=PA6+12% EPR1 impact modifier+organic stabilizer    -   Binder-NoPlast=Composition based on 48.8% PA612 (as defined        elsewhere), 30% PA6 (as defined elsewhere), and 20% EPR1 type        impact modifier, and 1.2% organic stabilizers.    -   EFEPc=Functionalized EFEP and Daikin Neoflon RP5000AS type        conductor    -   PA11-P=denotes a polyamide 11-based composition, containing 1%        plasticizer, 6% ethylene/ethyl acrylate/anhydride impact        modifier in a mass ratio of 68.5/30/1.5 (MFI 6 at 190° C. under        2.16 kg), and 1.2% organic stabilizers. The melting temperature        of this composition is 188° C.

Composition Constituents:

-   -   PA12: Polyamide 12 of Mn (number-average molecular mass) 35000.        The melting temperature is 178° C.; its melting enthalpy is 54        kJ/m2    -   PAU: Polyamide 11 of Mn (number-average molecular mass) 29000.        The melting temperature is 190° C.; its melting enthalpy is 56        kJ/m2    -   PA610: Polyamide 6.10 of Mn (number-average molecular        mass) 30000. The melting temperature is 223° C.; its melting        enthalpy is 61 kJ/m2    -   PA612: Polyamide 6.12 of Mn (number-average molecular        mass) 29000. The melting temperature is 218° C.; its melting        enthalpy is 67 kJ/m2    -   PA6: Polyamide 6 of Mn (number-average molecular mass) 28000.        The melting temperature is 220° C.; its melting enthalpy is 68        kJ/m2    -   EPR1: Designating an EPR functionalized by a reactive group with        anhydride function (at 0.5-1% by mass), of MFI 9 (at 230° C.,        below) 10 kg, of Exxellor® VA1801 from Exxon.    -   Organic stabilizer=1.2% organic stabilizers consisting of 0.8%        phenol (Lowinox® 44B25 from Great Lakes), 0.2% phosphite        (Irgafos® 168 from Ciba, 0.2% UV stabilizer (Tinuvin® 312 from        Ciba).    -   Plasticizer=BBSA (benzyl butyl sulfonamide)

1. A partially annulated flexible tubular structure located at leastpartially inside the fuel tank of a vehicle, said structure being atleast partially submerged in said tank and for use in transporting fuelinto said tank, said tubular structure comprising at least one layer (1)having a composition comprising: a. between 39% and 100% by weight, ofat least one aliphatic polyamide of formula W/Z wherein: W is analiphatic repeating unit obtained from the polycondensation of at leastone C6-C18 lactam, or at least one C6-C18 aminocarboxylic acid, or is analiphatic repeating unit XY having an average number of carbon atoms perdenoted nitrogen atom ranging from 6 to 18, obtained from thepolycondensation: at least one C6-C18 diamine X, said diamine beingselected from a linear or branched aliphatic diamine or a mixturethereof, and at least one C6-C18 aliphatic dicarboxylic acid Y, Z is atleast one optional polyamide repeating unit, Z present at up to 30% byweight relative to the total weight W/Z, b. between 0% and 4% by weightof at least one plasticizer, c. between 0% and 20% of at least oneimpact modifier, d. between 0% and 37% by weight of at least oneadditive, the sum of a.+b.+c.+d. being equal to 100%, excluding a fueltransport structure running from the tank to the motor of the vehicle.2. The tubular structure according to claim 1, wherein said at least onealiphatic polyamide is at least one polyamide denoted C obtained fromthe polycondensation of at least one C6-C18 lactam, or of at least oneC6-C18 aminocarboxylic acid, and having an average number of carbonatoms per nitrogen atom denoted CC ranging from 9 to
 18. 3. The tubularstructure according to claim 2, wherein said constituent a. of saidcomposition further comprises another polyamide selected from the groupconsisting of: at least one polyamide denoted A having an average numberof carbon atoms per nitrogen atom denoted CA ranging from 4 to 8.5; atleast one polyamide denoted B having a melting temperature higher thanor equal to 180° C. and an average number of carbon atoms per nitrogenatom denoted CB ranging from 7 to 10; and a mixture thereof, theweighted average mass of the melting enthalpies of the polyamides beinghigher than 25 J/g (DSC), the average number of carbon atoms pernitrogen atom of the polyamides A, B and C further satisfying thefollowing strict inequation: CA<CB<CC.
 4. The tubular structureaccording to claim 3, wherein the composition comprises between 34 and84% by weight of aliphatic polyamide C relative to the total weight ofthe polyamides present within said composition, preferably between 50and 80%.
 5. The tubular structure according to claim 3, whereinpolyamide A is selected from PA 6, PA 46 and PA 66, polyamide B isselected from PA 610, PA 612, and polyamide C is selected from PA 11 andPA
 12. 6. The tubular structure according to claim 1, wherein W in saidat least one aliphatic polyamide of formula W/Z is at least onealiphatic repeating unit XY, which is a polyamide denoted B′ having amelting temperature higher than or equal to 180° C., and an averagenumber of carbon atoms per nitrogen atom denoted CB′ ranging from 7 to10, or a polyamide denoted C′ having an average number of carbon atomsper nitrogen atom denoted CC′ ranging from 9 to
 18. 7. The tubularstructure according to claim 6, wherein said constituent a. of saidcomposition consisting of at least one aliphatic polyamide denoted B′ ordenoted C′ further comprises another polyamide selected from: at leastone polyamide denoted A having an average number of carbon atoms pernitrogen atom denoted CA ranging from 4 to 8.5; at least one polyamidedenoted B″ having a melting temperature higher than or equal to 180° C.and an average number of carbon atoms per nitrogen atom denoted CBranging from 7 to 10, when said aliphatic polyamide is C′, at least onepolyamide denoted C″ having an average number of carbon atoms pernitrogen atom denoted CC″ ranging from 9 to 18, when said aliphaticpolyamide is B′; or a mixture thereof, the weighted average mass of themelting enthalpies of the polyamides being higher than 25 J/g (DSC), theaverage number of carbon atoms per nitrogen atom in polyamides A, B′,B″, C′ and C″ further satisfying the following strict inequation: CA<CB″or CB″<CC′ or CC″.
 8. The tubular structure according to claim 6,wherein the composition comprises between 34 and 84% by weight ofaliphatic polyamide B′ or aliphatic polyamide C′ relative to the totalweight of the polyamides present within said composition.
 9. The tubularstructure according to claim 7, wherein polyamide A is selected from PA6, PA 46 and PA 66, polyamide B′ is selected from PA 610, PA 612,preferably PA 610, and polyamide C″ is selected from PA 11, PA 12, PA1012, PA 618 and PA 1010, or polyamide A is selected from PA 6, PA 46and PA 66, polyamide B″ is selected from PA 610, PA 612, preferably PA610 and polyamide C′ is selected from PA 1012, PA 618 and PA
 1010. 10.The tubular structure according to claim 1, wherein n that the additivesd. is selected from the group consisting of carbon black, graphite,graphene, carbon fibers, carbon nanotubes an antioxidant, a heatstabilizer, a UV absorber, a light stabilizer, a lubricant, an inorganicfiller, a fire-proofing agent, a nucleating agent, a dye, reinforcingfibers, a wax, and mixtures thereof.
 11. The tubular structure accordingto claim 10, wherein said additive comprises carbon black.
 12. Thetubular structure according to claim 11, wherein said composition ofsaid layer (1) comprises: a. between 39% and 95% by weight of at leastone aliphatic polyamide, b. between 0% and 4% by c. between 0% and 20%of at least one impact modifier, d. between 5% and 32% by weight ofcarbon black, and between 0 and 5% by weight of at least one additiveother than carbon black, graphite, graphene, carbon fibers and carbonnanotubes, the sum a.+b.+c.+d. being equal to 100%.
 13. The tubularstructure according to claim 11, wherein said composition of said layer(1) comprises: a. between 39% and 85% by weight of at least onealiphatic polyamide, b. between 0% and 4% by weight of a plasticizer, c.between 10% and 18% of at least one impact modifier, d. between 5% and32%, by weight of carbon black, and between 0 and 5% by weight of atleast one additive other than carbon black, graphite, graphene, carbonfibers and carbon nanotubes, the sum a.+b.+c.+d. being equal to 100%.14. The tubular structure according to claim 10, wherein said additiveis at least carbon nanotubes.
 15. The tubular structure according toclaim 14, wherein said composition of said layer (1) comprises: a.between 70% and 99.5% by weight of at least one aliphatic polyamide, b.between 0% and 4% by weight of a plasticizer, c. between 0% and 20% ofat least one impact modifier, d. between 0.5% and 10% by weight of anadditive which is carbon nanotubes, and between 0 and 19% by weight ofat least one additive other than carbon black, graphite, graphene,carbon fibers and carbon nanotubes, the sum a.+b.+c.+d. being equal to100%.
 16. The tubular structure according to claim 14 or 15, whereinsaid composition of said layer (1) comprises: a. between 70% and 89.5%weight of at least one aliphatic polyamide, b. between 0% and 4% byweight of a plasticizer, c. between 10% and 18% of at least one impactmodifier, d. between 0.5% and 10% by weight of carbon nanotubes, andbetween 0 and 19% by weight of at least one additive other than carbonblack, graphite, graphene, carbon fibers and carbon nanotubes, the suma.+b.+c.+d. being equal to 100%.
 17. The tubular structure according toclaim 1, wherein the layer (1) is devoid of plasticizer.
 18. The tubularstructure according to claim 1, wherein said structure is annulated overat least 10% of its length.
 19. The tubular structure according to claim1, wherein at least 90% of the length of said structure is inside thetank.
 20. The tubular structure according to claim 1, wherein at least30% of the length of said structure is submerged in the fuel.
 21. Thetubular structure according to claim 1, wherein said structure consistsof a single layer and is devoid of any additive selected from carbonblack, graphite, graphene, carbon fibers and carbon nanotubes.
 22. Thetubular structure according to claim 21, wherein the thickness of saidlayer (1) is at least 600 μm.
 23. The tubular structure according toclaim 1, wherein said structure comprises at least one second layer (2)that is conductive or non-conductive, said layer (1) being located aboveor below said layer (2).
 24. The tubular structure according to claim23, wherein said layer (1) is located above said layer (2).
 25. Thetubular structure according to claim 23, wherein said second layer (2)comprises at least one aliphatic polyamide or fluorinated materialsselected from the group consisting of polyvinylidene fluoride (PVDF),functionalized fluorinated materials, functionalizedethylene-tetrafluoroethylene (ETFE) copolymer, functionalizedethylene-tetrafluoroethylene-hexafluoropropylene (EFEP) copolymer, andtetrafluoroethylene-perfluoro (alkylvinyletherchlorotrifluoroethylene(CPT) copolymer.
 26. The tubular structure according to claim 23,wherein said structure is devoid of a barrier layer, said second layer(2) comprising at least one aliphatic polyamide.
 27. A method fortransporting fuels into a tank, comprising the step of transporting afuel through a tubular structure according to claim 1.